In a video encoding method typified by H.264 and H.265, intra-frame prediction is performed such that pixel values in relevant blocks as predicted in units of square blocks using pixels of neighboring blocks, have already been encoded and decoded, as reference pixel. After residual signals between pixel values and infra-predictive values are orthogonally transformed/quantized, coefficient scanning is applied, entropy encoding is performed, and thereby a bitstream is generated.
Non Patent Documents 1 and 3 and Patent Document 1 propose an approach in which non-square blocks are added to a conventional international standard encoding scheme and, after residual signals between pixel values and intra-predictive values are orthogonally transformed/quantized on a non-square basis, their coefficients are rearranged into a square format, coefficient scanning is then applied to conventional square blocks, and entropy encoding is performed.
Non Patent Document 2 proposes a direction-adaptive residual transform (hereinafter appropriately referred to as DART) based on intra-prediction modes instead of the conventional separation type DCT.